It is proposed to study the effect of variations in dietary fat and antioxidants on the incidence of spontaneous and induced cancer in mice. Diets containing low or high levels of fat (saturated fat, "monounsaturated fat" and polyunsaturated fat) and with or without added BHA-BHT antioxidant, will be fed to CD-1 and C3H mice to evaluate effects on spontaneous cancer incidence. In addition CD-1 mice of both sexes will be injected with 1, 2-dimethylhydrazine to study the effect of diet on the incidence of induced cancers. In addition, enzymatic and ultrastructural studies will be done on microsomes, mitochondria and membranes of animals on experimental diets to provide possible explanations for differences in tumor incidence.